Excavator linkage angle determination using a laser distance meter

Abstract

An excavator calibration framework comprises an excavator, a laser distance meter (LDM), and a laser reflector. The excavator comprises a linkage assembly (LA), implement, and controller. The LA comprises a boom with point B, stick coupled to point B, and four-bar linkage (4BL) including nodes D, F, G, and H (a dogbone linkage between nodes D and F). The laser reflector is disposed at node F. The nodes F, G, and the point B define an outer triangle BGF that defines with node D three inner triangles DGB, DBF, and DFG. The controller executes an iterative process including determining a node F position based on a LDM/laser reflector measurement signal, determining a node D position based on the node F position, and determining a dogbone angle BDF of DBF based on the node D position. The controller generates an actual dogbone angle based on a series of dogbone angles.

What is claimed is: 
     
       1. An excavator calibration framework comprising an excavator, a laser distance meter (LDM), and a laser reflector, wherein:
 the excavator comprises a machine chassis, an excavating linkage assembly, an excavating implement, and control architecture; 
 the excavating linkage assembly comprises an excavator boom, and an excavator stick, and a four-bar linkage that collectively define a plurality of linkage assembly positions; 
 the excavator stick is mechanically coupled to a terminal pivot point B of the excavator boom; 
 the four-bar linkage comprises a node D, a node F, a node G, and a node H, and linkages disposed therebetween, the linkage between the nodes D and F defining a dogbone linkage; 
 the LDM is configured to generate one or more measurement signals indicative of a distance and an angle between the LDM and the laser reflector; 
 an outer triangle BGF is defined between the node F, the terminal pivot point B, and the node G; 
 the outer triangle BGF comprises a first length BG, a second length BF i , a third length GF i ; 
 the node D is positioned within the outer triangle BGF and defines, with the outer triangle BGF, three inner triangles DGB, DBF, and DFG within the outer triangle BGF; 
 the control architecture comprises one or more linkage assembly actuators and an architecture controller programmed to execute an iterative process, the iterative process comprising:
 disposing the laser reflector at a position corresponding to the node F; 
 generating a measurement signal indicative of a distance and an angle between the LDM and the laser reflector; 
 determining a position of the node F based on the generated measurement signal; 
 determining the second length BF i  and the third length GF i  of the outer triangle BGF at least partially based on the position of the node F; 
 determining an angle BGD (θ BGD ) of the inner triangle DGB at least partially based on the second length BF i , and the third length GF i  of the outer triangle BGF; 
 determining a position of the node D at least partially based on the angle BGD (θ BGD ); 
 determining a length BD along the excavator stick between the terminal pivot point B and the node D at least partially based on the position of the node D; and 
 determining a dogbone angle BDF (θ BDF ) of the inner triangle DBF based on the length BD along the excavator stick, a dogbone length DF of the dogbone linkage of the four-bar linkage, and the second length BF i  of the outer triangle BGF, the dogbone angle BDF (θ BDF ) corresponding to an angular orientation of the dogbone linkage with respect to the length BD along the excavator stick; and 
 
 the architecture controller is further programmed to:
 repeat the iterative process i times until i passes an iterative threshold; 
 generate an actual dogbone angle BDF (θ BDF   actual ) based on a series of dogbone angles BDF determined from the iterative process; and 
 operate the excavator using the actual dogbone angle (θ BDF   actual ). 
 
 
     
     
       2. An excavator calibration framework as claimed in  claim 1 , wherein determining the angle BGD (θ BGD ) of the inner triangle DGB at least partially based on the second length BF i , and the third length GF i  of the outer triangle BGF is further based on:
 determining an angle BGF (θ BGF ) of the outer triangle BGF and an angle DGF (θ DGF ) of the inner triangle DFG, wherein:
 the angle BGF (θ BGF ) of the outer triangle BGF is based on the first length BG, the second length BF i , and the third length GF i , and a law of cosines; and 
 the angle DGF (θ DGF ) of the inner triangle DFG is based on a length DG, a length DF, and the third length GF i , and the law of cosines. 
 
 
     
     
       3. An excavator calibration framework as claimed in  claim 1 , wherein the iterative process comprising moving the excavating linkage assembly to align the node F with the LDM. 
     
     
       4. An excavator calibration framework as claimed in  claim 1 , wherein determining a position of the node F based on the generated measurement signal comprises determining a height Ĥ and a distance {circumflex over (D)} between the node F and the LDM based on a LDM distance signal D LDM  and an angle of inclination signal θ INC , such that
     {circumflex over (D)}=D   LDM  cos(θ INC ), and
 
     Ĥ=D   LDM  sin(θ INC );
 
 
       including an offset horizontal distance (D 0 ) and an offset vertical distance (H 0 ) between the terminal pivot point A of the excavator boom and a laser origin of the LDM. 
     
     
       5. An excavator calibration framework as claimed in  claim 1 , wherein:
 the machine chassis is mechanically coupled to a terminal pivot point A of the excavator boom; 
 a position of the terminal pivot point B with respect to the terminal pivot point A is identified; 
 a position of the node G with respect to the terminal pivot point A is identified such that a first length BG between the node G and the terminal pivot point B is identified. 
 
     
     
       6. An excavator calibration framework as claimed in  claim 5 , wherein determining the second length BF i  and the third length GF i  of the outer triangle is at least partially based on the position of the node F, the position of the terminal pivot point B, and the position of the node G, such that, for an ith iteration:
 the second length BF i  is a distance between the terminal pivot point B and the node F; and 
 the third length GF i  is a distance between the node G and the node F. 
 
     
     
       7. An excavator calibration framework as claimed in  claim 6 , wherein determining the angle BGD (θ BGD ) of the inner triangle DGB at least partially based on the second length BF i , and the third length GF i  of the outer triangle comprises:
 determining an angle BGF (θ BGF ) of the outer triangle BGF based on the first length BG, the second length BF i , the third length GF i , and a law of cosines; 
 determining an angle DGF (θ DGF ) of the inner triangle DFG based on the law of cosines and a set of legs defining the inner triangle DFG, the set of legs comprising the dogbone linkage, the third length GF i , and a length GD; and 
 subtracting the angle DGF (θ DGF ) from the angle BGF (θ BGF ). 
 
     
     
       8. An excavator calibration framework as claimed in  claim 7 , wherein determining the position of the node D comprises:
 determining a horizontal distance D x  and a vertical distance D y  between the node D and the terminal pivot point A of the excavator boom at least partially based on the angle BGD (θ BGD ) and a horizontal distance G x  and a vertical distance G y  between the node G and the terminal pivot point A of the excavator boom, through a following set of equations:
     D   y   =G   y −sin(θ BGD −θ S )* GD , and
 
     D   x   =G   x −cos(θ BGD −θ S )* GD;  
 
 
 
       where θ S  is angle of the excavator stick with respect to vertical V. 
     
     
       9. An excavator calibration framework as claimed in  claim 8 , wherein determining the dogbone angle BDF (θ BDF ) of the inner triangle DBF is further based on the law of cosines. 
     
     
       10. An excavator calibration framework as claimed in  claim 1 , wherein:
 an implement dynamic sensor is disposed on the dogbone linkage to generate a measured dogbone angle signal (θ BDF   measured ); and 
 the actual dogbone angle BDF (θ BDF   actual ) is compared with the measured dogbone angle signal to generate an offset dogbone angle (θ BDF   bias ) based on a following equation:
   θ BDF   bias =θ BDF   actual −θ BDF   measured .
 
 
 
     
     
       11. An excavator calibration framework as claimed in  claim 10 , wherein the implement dynamic sensor is calibrated based on the offset dogbone angle (θ BDF   bias ) to remove a bias due to the offset dogbone angle (θ BDF   bias ). 
     
     
       12. An excavator calibration framework as claimed in  claim 1 , wherein:
 the excavator stick comprises a terminal point and is mechanically coupled to the excavating implement through the terminal point; 
 the four-bar linkage and the excavator stick are mechanically coupled to the excavating implement through the terminal point; and 
 the node G is disposed at a position corresponding to the terminal point of the excavator stick to which the excavator stick is coupled to the excavating implement. 
 
     
     
       13. An excavator calibration framework comprising an excavator, a laser distance meter (LDM), and a laser reflector, wherein:
 the excavator comprises a machine chassis, an excavating linkage assembly, an excavating implement, and control architecture; 
 the excavating linkage assembly comprises an excavator boom, and an excavator stick, and a four-bar linkage that collectively define a plurality of linkage assembly positions; 
 the excavator stick is mechanically coupled to a terminal pivot point B of the excavator boom; 
 the four-bar linkage comprises a first node, a second node, a third node, and a fourth node with linkages disposed therebetween, the linkage disposed between the first node and the second node comprising a dogbone linkage; 
 the LDM is configured to generate one or more measurement signals indicative of a distance and an angle between the LDM and the laser reflector; 
 an outer triangle is defined between the second node, the terminal pivot point B, and the third node; 
 the outer triangle comprises a first length between the terminal pivot point B and the third node of the four-bar linkage, a second length between the terminal pivot point B and the second node of the four-bar linkage, and a third length between the second node and the third node of the four-bar linkage; 
 the first node is positioned within the outer triangle and defines, with the outer triangle, three inner triangles comprising a first inner triangle, a second inner triangle, and a third inner triangle within the outer triangle; 
 the control architecture comprises one or more linkage assembly actuators and an architecture controller programmed to execute an iterative process, the iterative process comprising:
 disposing the laser reflector at a position corresponding to the second node of the four-bar linkage; 
 generating a measurement signal indicative of a distance and an angle between the LDM and the laser reflector; 
 determining a position of the second node of the four-bar linkage based on the generated measurement signal; 
 determining the second length and the third length of the outer triangle at least partially based on the position of the second node of the four-bar linkage; 
 determining a first inner triangle angle of one of the first inner triangle defined between the terminal pivot point B, the terminal point G of the excavator stick, and the first node of the four-bar linkage at least partially based on the second length and the third length of the outer triangle; 
 determining a position of the first node of the four-bar linkage at least partially based on the first inner triangle angle; 
 determining an inner length along the excavator stick between the terminal pivot point B and the first node of the four-bar linkage at least partially based on the position of the first node of the four-bar linkage; and 
 determining a dogbone angle defined by the second inner triangle, the second inner triangle formed from the inner length along the excavator stick, a dogbone length of the dogbone linkage of the four-bar linkage, and the second length of the outer triangle, the dogbone angle corresponding to an angular orientation of the dogbone linkage with respect to the inner length along the excavator stick; and 
 
 the architecture controller is further programmed to:
 repeat the iterative process i times until i passes an iterative threshold; 
 generate an actual dogbone angle based on a series of dogbone angles determined from the iterative process; and 
 operate the excavator using the actual dogbone angle. 
 
 
     
     
       14. An excavator calibration framework as claimed in  claim 13 , wherein the first node is a node D of the four-bar linkage, the second node is a node F of the four-bar linkage, the third node is a node G of the four-bar linkage, and the fourth node is a node H of the four-bar linkage. 
     
     
       15. An excavator calibration framework as claimed in  claim 14 , wherein the outer triangle is a triangle BGF, the first length of the outer triangle is a first length BG, the second length of the outer triangle is a second length BF i , and the third length of the outer triangle is a third length GF i . 
     
     
       16. An excavator calibration framework as claimed in  claim 15 , wherein:
 the first inner triangle comprises an inner triangle DGB, the second inner triangle comprises an inner triangle DBF, and the third inner triangle comprises an inner triangle DFG; 
 the first inner triangle angle comprises an angle BGD of the inner triangle DGB; and 
 the dogbone angle comprises a dogbone angle BDF of the inner triangle DBF. 
 
     
     
       17. An excavator calibration framework comprising an excavator, a laser distance meter (LDM), and a laser reflector, wherein:
 the excavator comprises a machine chassis, an excavating linkage assembly, an excavating implement, and control architecture; 
 the excavating linkage assembly comprises an excavator boom, and an excavator stick, and a four-bar linkage that collectively define a plurality of linkage assembly positions; 
 the excavator stick is mechanically coupled to a terminal pivot point B of the excavator boom; 
 the four-bar linkage comprises a node D, a node F, a node G, and a node H, and linkages disposed therebetween, the linkage between the nodes D and F defining a dogbone linkage, the laser reflector disposed at a position corresponding to the node F, the nodes F, G, and the terminal pivot point B defining an outer triangle BGF, and the node D positioned within the outer triangle BGF to define three inner triangles DGB, DBF, and DFG; 
 the LDM is configured to generate one or more measurement signals indicative of a distance and an angle between the LDM and the laser reflector; 
 the control architecture comprises one or more linkage assembly actuators and an architecture controller programmed to execute an iterative process, the iterative process comprising:
 determining a position of the node F based on a generated measurement signal indicative of a distance and an angle between the LDM and the laser reflector; 
 determining a position of the node D at least partially based on the position of the node F; 
 determining a dogbone angle BDF of the inner triangle DBF at least partially based on the position of the node D; and 
 
 the architecture controller is further programmed to:
 repeat the iterative process i times until i passes an iterative threshold; 
 generate an actual dogbone angle BDF based on a series of dogbone angles BDF determined from the iterative process; and 
 operate the excavator using the actual dogbone angle. 
 
 
     
     
       18. An excavator calibration framework as claimed in  claim 17 , wherein:
 the outer triangle BGF comprises a first length BG, a second length BF i , a third length GF i ; and 
 determining a position of the node D at least partially based on the position of the node F comprises:
 determining the second length BF i  and the third length GF i  of the outer triangle at least partially based on the position of the node F; 
 determining an angle BGD of one of the inner triangles DGB at least partially based on the second length BF i , and the third length GF i  of the outer triangle; and 
 determining a position of the node D at least partially based on the angle BGD. 
 
 
     
     
       19. An excavator calibration framework as claimed in  claim 18 , wherein determining a dogbone angle BDF of another of the inner triangles DBF at least partially based on based on the position of the node D comprises:
 determining a length BD between the terminal pivot point B and the node D at least partially based on the position of the node D; and 
 determining a dogbone angle BDF of another of the inner triangles DBF at least partially based on based on the length BD, a dogbone length DF of the dogbone linkage of the four-bar linkage, and the second length BF i  of the outer triangle BGF. 
 
     
     
       20. An excavator calibration framework as claimed in  claim 17 , wherein:
 the machine chassis is mechanically coupled to a terminal pivot point A of the excavator boom; 
 a position of the terminal pivot point B with respect to the terminal pivot point A is identified; 
 a position of the node G with respect to the terminal pivot point A is identified such that a first length BG between the node G and the terminal pivot point B is identified.